A multiple-input multiple-output (MIMO) wireless communication system can utilize multiple antennas at both a transmitter and a receiver to transmit and receive data and to improve the range and performance of the system. Data packets can be independently and simultaneously transmitted in parallel using separate MIMO channel subcarriers on different transmission antennas. At each receiver antenna, the independent data packets can be combined and the receiver can recover the separate data signals with a decoder. Data transmitted and received using a MIMO system can be modulated using orthogonal frequency division multiplexing (OFDM) or other modulation schemes. Examples of MIMO-OFDM systems include wireless local area networking using the IEEE 802.11n standard, wireless metropolitan area networking using the IEEE 802.16e/j/m standards, mobile phone communications using the 3GPP LTE standard, and other systems.
In a MIMO system, the transmitter can utilize channel state information of a channel subcarrier to perform transmit beamforming. Transmit beamforming is a technique that can increase the directivity of transmitted data packets and the signal-to-noise ratio gain at the receiver. Channel state information can be maintained by the transmitter using explicit beamforming, where the transmitter sends a sounding packet to the receiver, and in response the receiver feeds back steering matrix information to the transmitter.
However, problems can arise when the receiver feeds back steering matrix information to the transmitter. One such problem is that the receiver may not have full information regarding how the sounding packet was generated, such as particular settings or matrices used by the transmitter in generating the sounding packet. This lack of information can result in situations where the receiver feeds back incorrect steering matrix information that can cause a power imbalance between transmitters in the MIMO system, resulting in a reduction of the transmitter's transmit power.